Earth had several tiny hidden moons billions of years ago, study suggests

Our current Earth-Moon system was formed when a protoplanet named Theia smashed into our planet some 4.5 billion years ago. This is when Earth was just 100 million years old. The collision ejected loads of debris, some of which came back to Earth while the rest created our lunar satellite. Scientists have been studying this phenomenon and its consequences for years. They have even discovered possible remnants of Theia within the Earth’s mantle. The Moon, some scientists believe, was formed only in a matter of few hours.

Now a new study by scientists at the University of Nevada suggests that the aftermath of the collision likely led to the creation of not one but many moons. These results are available on the non-peer-reviewed preprint server arXiv. According to the study, these were a variety of polar moons—also known as circumbinary particles—that lingered around only for a short period of time. As per the scientists, the existence of these “moons” was possible only because of the close proximity of the Moon to Earth. Notably, at 238,900 miles on average, the Moon in its first few hours of coming to life sat only five per cent as far from Earth as its present distance.

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“Circumbinary orbits that are polar or highly inclined to the Earth-Moon orbit are subject to two competing effects: nodal precession about the Earth-Moon eccentricity vector and Kozai-Lidov oscillations of eccentricity and inclination driven by the Sun,” the paper reads.

“While we find that there are no stable polar orbits around the Earth-Moon orbit with the current day semi-major axis, polar orbits were stable immediately after the formation of the Moon, at the time when there was a lot of debris around the system.”

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Earth moved away from us

Nodal precession means that a body’s orbital parameters undergo a slow change around the angular moment vector. Kozai-Lidov oscillations involve a binary system and the perturbations introduced by a distant third body. Taking these factors into consideration, they deduced that the particles orbiting in the polar region were the most stable. This is directly linked to the earliest distance of the Moon from Earth. The Moon later started moving away from us because of the tidal forces.

“If a significant mass of material ended up on polar or librating orbits, then the eccentricity of the Earth-Moon binary could have been increased as a result of its interaction.”

The latest theory can help scientists learn more about the exoplanets outside our solar system.